Plug fuse



Dec.z8, 1937. E A, G GANOE 2,103,717

PLUG FUSE l Filed July 6, 1935 f4 24@ i /3 Si.

15 1 N V E NTOR.

/Ww ATTORNEYs Patented Dec. 28, 1937 UNITED STATES PATENT OFFICE PLUG FUSE Application July 6, 1935, Serial No. 30,007

Claims.

This invention relates to plug fuses and contemplates an improved plug fuse structure particularly suited for present day commercial manufacture.

Plug fuses have been used for many years. The fuse is a plug structure having a cavity which contains a fuse link; there is a window through which the link can be observed; and the link is electrically connected to an exterior center con- 10 tact and an exterior screw contact. In general, plug fuses have been made in two ways. `One of the ways is by forming the body portion of the plug as an open topped cup of porcelain or Bakelite, and closing the cap by a mica or glass disc secured in place by a crimped metal band that embraces the top of the plug. This form of fuse body is simple in design, but the metal band is objectionable in that it must be grasped with the hand in inserting the fuse and involves a certain degree of hazard due to the electric conductivity of the band and sharp burrs which may occur on it. The other plug fuse construction that has been generally used involves an inverted glass cup which provides the fuse link cavity and through which the fuse link can be observed. This construction requires a separate bottom piece of porcelain or Bakelite that has to be cemented or otherwise secured to the inverted glass cup. This involves obvious manufacturing disadvantages, and sometimes results in a somewhat fragile fuse.

An object of the present invention is to provide a fuse plug having the advantages of the open topped cup body without the disadvantages that have heretofore existed with such type of construction.

Another object of the present invention is to provide a sturdy, reliable fuse plug that meets the requirements of commercial manufacture from the standpoint of cost, ease and rapidity of manufacture, accuracy, small percentage of bad fuses, etc.

Of course, plug fuses may be used in any position as far as up-side-down or right-side-up is concerned, but for the sake or convenience, the

drawing illustrates the fuse, and it will be described throughout, on the assumption that the axis of the plug is standing vertically with the window lying in a horizontal plane at the top so of the fuse.

Fig. I is a central vertical section of a complete plug fuse embodying the present invention.

Fig. II is a plan View with large portions of the top structure broken away to disclose the interior of the plug.

(Cl. ZOO-) Fig. III is a bottom View of the complete fuse.

Fig. IV is a detailed sectional View taken on the line 4 4 of 1Eig. II.

Fig. V is a view ci the closure retaining member of the fuse, part of the view being in central 5 vertical section, and part of the view being in elevation.

Fig. VI is an elevation of the lower portion of the plug body.

In the original bristol board drawings led in l0 the Patent Oflice all of the iigures are on an enlarged scale, being much larger than the coinmercial fuse from which they were made. The particular fuse illustrated in the drawings is for use with a receptacle equipped with a circuit 15 breaking adapter, e. g. the receptacle shown in Moore Patent 1,990,953v issued February 12, 1935, but many of the advantageous features of the present construction may also be utilized in plug fuses designed for the standard Edison base J socket.

Referring to the drawing, the plug fuse is built up about a body portion designated as a whole by I, which consists of a single piece of molded insulating material such as a suitable 25 phenol condensation product. The body I is cupshaped, having an annular wall 2 which surrounds a cavity 3, and having a transverse portion 4 which forms the bottom of the cup-shaped formation. A skirt 6 depends from the bottom 30 of the cup formation and is molded with threads 'I on its exterior surface, as is more clearly shown in Fig. VI. The upper portion of the fuse body is formed with two concentric walls 8 and 9 separated by an annular space. The exterior 35 surface of the outer wall 9 is serrated at 5fL to form a hand grip for manipulating the fuse; and the interior surface of the wall 9 is annularly relieved or recessed at 9b to receive a retainer which will be referred to later. While newly 40 molded phenol condensation product is still hot after being heated in the mold, it is somewhat elastic and this permits the body I to be stripped from the mold despite the annular recess 9b.

A plurality of transverse radial notches I0 are 45 formed in the top of wall 8; and from the bottom of the annular space between Walls 8 and 9, a plurality of apertures II extend downwardly to the exterior of the plug body. Molded into the body I is a channel I2 extending downwardly from the 50 top of wall 8 on the interior of the body, and aligned with the channel I2 is a second molded channel I3 which extends upwardly on the exterior of the body. These two channels intersect withone another sufficiently to provide a 55 narrow passageway from the cavity 3 to the exterior of the body. The bottom 4 of the cavity 3 is formed with an apertured depressed center portion 4a, and in the wall of the aperture are four vertical grooves 5b. vertical grooves lb intersect with horizontal grooves It, that are on the bottom of body portion te. On the top of body portion lia there are radially extending grooves 4d positioned between vertical grooves tb.

A copper contact button I6 has a shank il which is initially tubular, like a tubular rivet. After the shank Il has been inserted through the aperture of the body portion lia, portions of the shank are stamped outwardly at I'Ia into the horizontal channels lid, thus Xedly securing the contact button in place. A fuse link IS has one end soldered to the contact button I6 and passes downwardly to the exterior of the body I through the aperture provided by the meeting of channels I2 and i3. Ir desired, suitable cement may be used at I 8a to seal the opening through which link IS passes. A threaded metal ferrule I9 is Screwed onto the threads I of the plug body, and the fuse link i8 is soldered to this errule. A portion ma of the ferruleis struck into a notch 6a on the plug body, thereby preventing unscrewing of the ferrule.

A closure disc 22 ofsuitable material such as glass or mica is placed on top of wall 8, which acts as a means for supporting the closure disc. Then, a closure retainer, designated as a whole Vby 23 is applied on top of the closure disc Y22 and secures it in place. This retainer 23 is a single piece of springy sheet metal, having an inwardly extending annular flange 2li and a depending skirt 25 that is folded back upwardly at 25a. The edgeportion 25a is flared outwardly, so that when the retainer is applied as shown in Fig. I this edge engages in the annular recess 9b and locks the retainer and the closure disc 22 in place. The skirt portion 25a is usually a continuous annular metal band, but in the alternative, vertical slits such as 25c may be provided to increase the yielding range of the skirt if desired. The flan-ge 24 inclines downwardly as it progresses inwardly; and the very edge portion 24a of the ange may be additionally depressed if desired. When the Vretainer is applied the edge portion 24a strikes the closure disc 22 and yields upwardly, thus clamping the closure 22 under yielding spring pressure. This provides a degree of adjustment to take care of manufacturing variations in the location of annular recess 9b and the thickness of the glass or mica 22.

When the fuse blows, considerable hot gas is generated and this is vented throughV tortuous passages which cool the gas and prevent any danger of damage. From the cavity 3 gases may pass downwardly through the vertical grooves 4b and outwardly through connecting horizontal grooves la Also, gases pass through notches iii tothe annular space between walls 8 and 9, and out to the open air through downwardly extending passageways i I. The edge of the retainer 23 may make a fairly tight t with the annular groove 9b, thus preventing substantial yescape of gases to the top of the fuse on the exterior of the retainer 23 (unless slits 25c are used). Also edge 2da of the retainer may make a tight fit with the top of the closure disc 22, thereby preventing escape of gases to the top of the inside of the retainer.

The manufacturers name, voltage and amperage rating of the fuse, etc., may be placed At their lower ends the by a label or otherwise upon the portion 243 of the retainer. In manipulating the fuse, it is handled only by the insulated grip ea and no metal comes in contact with the hands. It will be seen that the construction is very simple and prac-t tical, being assembled about a one piece body of molded insulation without the necessity for cement or questionable attachments at any point.

In compliance with the patent statutes, I have disclosed the best form in which have contenidplated applying my invention, but it will be reale' ized that many variations may be made within the scope of the claims.

What is claimed is:

l. A plug fuse comprising: a one-piece, cupshaped body of molded insulating material, the body having an annular hand grip adjacent to its upper end and exterior threads adjacent to its lower end, and having within the cavity cf the cup formation annularly located closure supporting means; a threaded contact thimble screwed onto the threaded portion of the body; a closure disc entering the cavity oi the cup formation and resting against said closure supporting means; and closure retaining means removed from the hand grip portion of the body and located wholly within the space encircled by the hand grip, the closure retaining means be'- ing an annular sheet metal member that makes spring contact with the top of the closure disc, and also encircles the closure disc and depends below it to prevent the fuse gases from escaping to the top of the fuse. I

2. An annular body for a plug fuse, the body having an open end adjacent to which there arev two spaced concentric walls providing an annular channel between the walls, the top of the inner wall being adapted to receive Va closure dise and the channel between walls being adapted to receive a closure retainer.

3. An annular body for a plug fuse, the bodyy having an open end adjacent to which there are two spaced concentric walls providing an annular channel between the walls, the inner wall having venting passages leading to said annular channel, and the interior surface of the outer wall being recessed to receive a closure retainer.

4. A plug fuse body consisting of a single cupshaped piece of molded insulating material, the body having adjacent to the mouth of the cup i'ormation two spaced concentric walls providing an annular channel between the walls, the exterior of the outer wall being formed as a hand grip, the top of the` inner wall being formed to support a closure disc, and the channel between f walls being formed to receive a closure retainer.

5. A plug inse body consisting of a single piece of hollow molded insulating material, the body having an open end adjacent to which there are two spaced concentric walls, the top of the inner wall being at a lower level than the top` of the outer wall and being provided with venting notches leading to the space between walls, there being additional venting passages leading from the space between walls to the exterior of the body.

6. A plug fuse comprising: a body consisting of a single piece of hollow molded insulating material, the body having an open end adjacent to which are two spaced concentric walls, the eX- terior of the outer wall being formed as a hand grip, and the top of the inner wall being positioned to support a closure disc; a closure disc resting against the top of therinner Wall; and a springy closure retainer having an annular flange overlying the closure disc and having a skirt depending into the space between the concentric walls.

'7. For a plug fuse, a closure disc retainer consisting of a spring piece of sheet metal having an inwardly extending annular flange portion to engage the closure disc7 and having an annular portion depending from said ange portion, said depending portion comprising two spaced annular walls resiliently connected together.

8, A plug fuse comprising: a body having means to support a closure disc and means to intert with a closure disc retainer; a closure disc supn ported by the supporting means oi the body; and a closure disc retainer securing the closure disc to the body, the retainer consisting of a springy piece of sheet metal having a skirt portion provided with means to make snap engagement with the intertting means on the body, and having an annular inwardly extending flange portion to resilently engage the closure disc.

9. A plug fuse comprising: a body having means to support a closure disc and means to intert with a closure disc retainer; a closure disc supported by the supporting means of the body; and a closure disc retainer securing the closure disc to the body, the retainer consisting of a springy piece of sheet metal having a skirt p01'- tion provided with means to make snap engagement with the intertting means on the body, and having an annular inwardly extending flange portion to engage the closure disc, the interior edge of the ange portion being depressed to enable the retainer to yieldingly accommodate manufacturing variations in the thickness of the closure dise.

l0. A plug fuse comprising: a body having means to support a closure disc and means to intert with a closure disc retainer; a closure d isc supported by the supporting means of the body; and a closure disc retainer securing the disc to the body, the retainer` consisting of a unitary piece oi' springy sheet metal provided with means to make snap engagement with the intertting means on the body, and having a portion to resiliently engage the closure disc.

ERNST A. Gr. GANOE. 

